Problem: $ { {-1} \times \left[\begin{array}{rr}{-2} & {0} \\ {1} & {3}\end{array}\right] = {?} } $
Explanation: To multiply a matrix by a number, multiply each item of the matrix by the number. ${\left[\begin{array}{rr}{-1}\times{-2} & {-1}\times{0} \\ {-1}\times{1} & {-1}\times{3}\end{array}\right]}$ Now, simplify: ${\left[\begin{array}{rr}{2} & {0} \\ {-1} & {-3}\end{array}\right]}$